Noise eliminator for telephone transmitters



Aug. 5, 1947. H. J. HART 2,425,051

NOISE ELIMINATOR FOR TELEPHONE TRANSMITTER'S Filed Dec. 16, 1945 Patented Aug. v5, 1947 OFFICE NOISE -ELIlWINA-TOR FOR TELEPHONE TRANSMITTERS Harry J. Hart, Baldwin-Township, Allegheny County, Pa.

Application December 16, 1943, Serial No. 514,475A

My invention relates to telephones, and .con-v sists in an appliance for excluding extraneous noises from the transmitter of a telephone instrument.

A sound-excluding or eliminating .appliance of the type to which this invention relates consists essentially in perforated sound screen that is adapted to be secured over the transmitter of a telephone instrument. Organized with the sound screen is a shutter which by manipulation may be caused to close the perforations in the screen. Thus, when the user of the telephone is not talking, he may exclude all sound from the transmitter of the telephone instrument, with the effect that he obtains better reception of the message transmitted to him. Of course, when the user'of the `telephone vis speaking, the shutter is so posi- Y tioned as to uncover the perforations. In general, an appliance or device of this sort is years old` in the art, and it is to be understood that my invention relates to certain new and useful improvements in the construction of suchl an appliance and in the particular structural organi- Zation of the appliance with a modern telephone instrument, whereby the appliance becomes commercially practical and valuable.

The invention will be understood upon reference to the accompanying drawings, in which:

Figure 1 is aview in front elevation of the receiver-transmitter unit of a modern telephone instrument. The unit is shown held in the hand l of a user, and on the transmitter portion of the unit is shown a sound-eliminator of the present invention;

Figure 2 is a view in plan and to larger of the outer side of the sound-eliminator;

Figure 3 is a view in plan of the same as seen from the inner side; n Y

Figure 4 is a view in medial sectionand to still larger scale of the sound-eliminator, the transmitter portion ofthe receiver-transmitter uni-t vscale on which the device is adapted to Abe seouredloe-v ing shown in broken lines; and K Figure `5 kis a fragmentary view, corresponding. to Figure 4, and illustrating a modiiicatio'n or elaboration in structure.

`Referring to the drawings, the reference .numerall is .applied to the receiver-transmitter unit of a conventional telephone instrument, and .3

indicates generally a sound-eliminatorof the invention. The sound-eliminator comprises a cap that includes a perforate diaphragm'portionl f having a skirt portion 5 provided internally with a peripheral bead that engages the usual groove 'I (Figure 4) formed in the cover or housing 8 on 8 Claims. '(Cl. 179-188) Lorate face of the transmitter housing or casing 8. Means are provided for opening and closing the Lperforations of the sound screen, whereby the sound screen may, at the will of the person Vusing ythe telephone, be effective to exclude sound "from the transmitter, or to permit the entrance of sound, i. e., sound waves.

Such means comprise a-perforate shutter disk 9 .mounted within the-body 4, 5 to turn on a post Ill. The -s-hutter disk is provided with an arm I I extending through a circumferential slot I2 in the skirt portion 5, and as thus extending the arm H is accessible to the nger F of the hand of theperson using the telephone. The soundeliminator is, it will be seen, so positioned on the transmitter portion of the telephone unit 2 that the arm I'I maybe readily manipulated by the nger F of the rhand vthat holds the receivertransmitter Kunit of the telephone, whereby the other hand of the telephone user remains .free to write memoranda, etc., while 4using-the telephone. Thisis an important advantage of the structural organizationof my invention.

The perforations I3 in the shutter 9 are identi- ,cal in form and arrangement to the perforations III on` vthe screen 4, and a torsion spring I5, secured in a lsuitable kerfV inthe post I0, includes two oppositely extending portions having upturned ltips ld-(Figures 4and 5) that are lodged in, two of the perforations |.l3 in the shutterdisk,l the spring being stressed before the tips .are sprung into the perforations. The spring exerts a constant torsional stress, tending to rotate the shutterclockwisefas it appears in Figure 2. Under the stress of thespring the shutter is normally maintained in a Yposition with Vthe arm l I bearing .against the right-hand end of the slot I2 (Figures 1.and 2), and in such position the periorationsor orices'lan-d .It of the shutter and screen,I respectively, stand in exact registry (see Figure 4), whereby the voice `oi a Aperson speaking into. the transmitter of the telephone instrumen-t is clearly .transmitted over the telephone system. Alternately, when the telephone .user is listening Ato -a message .received by the receiver portion 8D .of the' unit 2,V he presses-his finger against the arm -II and thereby turns the shutter 9 into a position Ain which the'body portions of the shutter between the perforations 'I3 close all oi the perforations I4 in thescreen ll. Thus,

the screen 4 becomes an impervious diaphragm,

excluding all external noises from the transmitter portion of the telephone instrument, whereby the telephone circuit is protected from the effeet of extraneous sound waves. The spring I5, anchored to the post ID serves in a second capacity; that is, it serves to secure the shutter 9 in assembled position upon the post I0.

At this point it may be noted that the particular arrangement and graduated size of the perforations in the screen 4 and shutter '9 are important. The -perforations adjacent the common center of the assembled members 4 and v9 are smallest, there being an inner ring of nine per- Y forations of als" in diameter. Outward from such inner ring is a second ring of nine perforations of 1/8" in diameter; outward from the secshall be distributed radially and circumferentially of the center of the assembly, and the effective area of the openings is greater according as the radial distance of the openings from said center is greater.

A valuable feature of the structure comprises a gasket 9b that is secured in a peripheral channel 9a in the shutter disk 9. This gasket is formed of a compressible, sound-absorbing material such as felt. When the sound-eliminating device is assembled in service position, this gasket bears upon the surface of the transmitter housing 9 (Figure 4). The gasket encompasses the usual perforations (not shown) formed on the face of the transmitter housing, and insures the exclusion of all sound waves therefrom, except the sound waves that are intentionally permitted to pass through the perforations I3 and I4. The gasket 9b while affording sound-tight assembly of the device upon the transmitter housing, in no way interferes with the desired manipulation of the shutter disk.

The acoustic properties of the device are further enhanced by the provision of a coating 9c (Figure 3) of sound-absorbing material upon the inner face of the shutter disk. This coating may comprise small particles of felt dusted upon a film of adhesive, such as a resinous glue, applied to the surface of the disk.

An important feature of the sound-eliminator of my invention consists in its structural form which permits manufacture from a plastic material, particularly a molding or moldable plastic material. Any one of the several known molding plastic materials may be used, say urea formaldehyde, yor a phenolic, a vinyl, or other suitable resin. Manifestly, the shutter disk 9 may be readily produced in a plastic-molding press. In the case of the portion 4, 5 of the device, the molding operation may be facilitated by the pro- Vision of a plurality of slits I6 that opens inward from the rim of the skirt portion 5. The slits are herein shown to` be four in number, spaced ninety degrees apart. By Virtue of these slits the molded body 4, 5 may be more readily stripped from that die portion of the molding press which includes the groove for forrningthe bead 6 on the skirt, the molded and curedv plas- 75 annular side of the casing surrounding said face,

tic material possessing adequate elasticity to permit such stripping away of the formed article. Additionally, and of at least equal importance, the provision of the slits I6 provides in the skirt `5 a yieldability that more readily permits the skirt to expand radially as the device is applied to the transmitter portion 8, and when the bead 6 reaches the groove 1 in the portion 8, the inherent elasticity of the skirt causes the expanded skirt to contract, locking the bead 6 in the groove 'I. Security of attachment of the applied soundeliminator is thus obtained.

In elaboration of the structure described, I -provide a detent I1 in the body of the sound-eliminator. This detent comprises a pin organized with a spring I8 that tends to hold the pin in its illustrated position. The inner end of the pin is provided with ahead I9 that provides an abutment limiting the outward movement of the pin under the stress of spring I8. The pin is so located in the path of movement of the arm II of the shutter, that when the shutter is moved into closed position, the pin may be pressed inward to engage the arm II and prevent the shutter from returning to normal position in which the perforations I3 and I4 stand in registry. When the pin is thus vpressed inward, the head I9 on the pin latches beneath the engaged edge of the arm II, and holds the pin, against the stress of spring I8, in arm-engaging position. When the shutter is locked in closed position, there will be a slight clearance between the end of slot I2 and the adjacent edge of arm II, so that to release the shutter it will be merely necessary to press the arm II in shutter-closing direction through the interval permitted by said slight clearance, such movement of the arm releasing the engagement of the pin head I9 with l the arm, whereby the pin returns to normal position under the eifect of spring I8.

The provision of the detent I'I-IS permits the user of the telephone to lock the shutter in closed position for an interval of time, as may be desirable when the user must interrupt a telephone conversation and lay the receiver-transmitter unit 2 aside while he looks up certain information or performs some task. In this way the telephone circuit may be protected from the noises prevailing in the room in which the telephone instrument is located. The reader need only to call to YInind the noise in a machine shop, or the like,v toappreciate the value of the structure described.

Within the terms of the appended claims many modifications and variations are possible, Without departing from the spirit of the invention.

I claim as my invention:

1. An `appliance for a telephone transmitter having a casing that includes a perforate circular face and a circumferential groove in the annular side of the casing surrounding said face, said appliance comprising a cap member adapted to be assembled over said transmitter casing, said cap member having a perforate diaphragm portion arranged in assembly to overlie the percap member in assembly therewith.

2. ,An appliance for a telephone transmitter having a casing that includes a perforate Vcircular face and a circumferential groove in the said appliance comprising a cap member adapted to be assembled over said transmitter casing, said cap member comprising an integrally molded body of plastic material having a perforate diaphragm portion arranged in assembly to overlie the perforate face of said casing and a radially expansible elastic skirt portion extending peripherally of the diaphragm portion, said skirtrfportion including a plurality of slots extending in- Ward from the edge thereof at circumferentially spaced-apart points, the slotted skirt portion carrying at its peripheral edge means for yieldingly engaging said groove in said casing to secure the cap member in assembly therewith.

3. In the combination of a receiver-transmitter telephone unit and a noise eliminator including a perforate sound screen applied upon the transmitter portion of said unit, said noise eliminator including a shutter movable between alternate positions to open and close the perforations in said screen, a sound-absorbing gasket carried by the periphery of said movable shutter and bearing upon the body of the transmitter portion of said unit, a torsion spring urging said shutter into one of said positions, said shutter having a member extending therefrom in position to be manipulated by a finger of the hand holding the receiver-transmitter unit in service to move said shutter into the other of said positions.

4. In the combination of a receiver-transmitter telephone unit and a noise eliminator including a perforate sound screen applied upon the transmitter portion of said unit, said noise eliminator including a shutter movable to open and close the perforations in said screen, a sound-absorbing gasket carried by the periphery of said movable shutter and bearing upon the body of the transmitter portion of said unit, a coating of soundabsorbing material carried by said shutter, said shutter having a member extending therefrom in position to be manipulated by a finger of the hand holding the receiver-transmitter unit in service.

5. In combination a receiver-transmitter telephone unit and a noise eliminator including a perforate sound screen applied upon the transmitter portion of said unit, said noise eliminator including a shutter movable to open and close the perforations in said screen, a spring normally urging said shutter into perforation-opening position, and means included in the noise eliminator` structure for temporarily locking said shutter against spring tension in closed position.

6. An appliance for a telephone transmitter Whose perforate mouth-piece includes a peripheral groove, said appliance comprising a perforate sound screen having an elastic skirt includinga rib adapted to engage said groove in the mouthpiece, and a manually operable shutter for opening and closing the perforations in said screen, said movable shutter carrying a sound-absorbing gasket bearing slidably upon the mouth-piece in encompassing relation with respect to the mouth-piece perforations.

7. An appliance for a telephone transmitter having a perforate mouth-piece, said appliance comprising Aa perforate sound screen and means for securing it upon said perforate mouth-piece, and a manually operable shutter for opening and closing the perforations in said screen, said movable shutter carrying a sound-absorbing gasket bearing slidably upon said mouth-piece in encompassing relation with respect to the mouthpiece perforations.

8. An appliance for a telephone transmitter having a periorate mouth-piece, said appliance comprising a perforate sound screen and means for securing it upon said perforate mouth-piece, a manually operable shutter for opening and closing the perforations in said screen, a spring normally urging said shutter into perforationopening position and means included in the appliance structure for temporarily locking said shutter in against spring tension position with the screen perforations closed.

HARRY J. HART.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,726,855 Parker Sept. 3, 1929 1,225,672 Nakai May 8, 1917 1,611,948 Reid Dec. 28, 1926 2,080,552 Whittaker May 18, 1937 933,228 Burkholder Sept. '7, 1909 1,884,724 Keller Oct. 25, 1932 831,889 Patterson Sept. 23, 1906 

